1. Field of the Invention
The present invention relates to a colored film, a colored film-attached glass product and a process for producing the product. Particularly, it relates to a colored film which provides an excellent ornamental property and protection of privacy and is suitable for various glass surfaces for automobiles, buildings, etc., a glass product provided with such a colored film, and a process for producing such a product.
2. Description of the Background
Many methods have been proposed to impart various functions by forming metal oxide coating films on substrates. Methods for forming coating films which are commonly used at present, include, for example, a dry method such as vacuum deposition, sputtering or CVD, and a wet method such as a sol-gel method or a spray thermal decomposition method. Among them, formation of a metal oxide film by a wet method is industrially advantageous, since film formation can be carried out at a low cost. When a glass surface is coated with a thin film of a transition metal oxide, the glass will be colored variously due to the ion absorption. Further, as a characteristic of the light absorptive oxide, the reflectance will be increased to present a half mirror state, whereby the ornamental property of the glass will be improved.
As a method for forming a metal oxide coating film by a wet method, a method has heretofore been known in which a liquid prepared by a so-called sol-gel method, containing a metal alkoxide as the main material, is coated. However, in the case of a sol-gel method using a metal alkoxide as the main material, the color which can be developed, is limited, and it has been difficult to obtain a film which exhibits a desired color clearly, and there has been another problem that the film is not practically useful from the viewpoint of chemical resistance or abrasion resistance.
On the other hand, a method has been proposed in which a metal salt and a silicon alkoxide or the like are mixed, followed by film forming by a sol-gel method (e.g. J. Non-Crystalline Solids 82 (1986) 378-390). However, such a method has had a problem that if a silicon alkoxide or the like other than the coloring component is added to such an extent that the resulting coating film will have adequate durability, the absorbance decreases, and the desired colored film can not be obtained, and further it tends to be difficult to obtain a clear color.
On the other hand, a demand has recently increased for a variety of colors for colored films, and uniformly colored films having not only a conventional gray or bronze color but also a primary color such as red, blue or green, or an intermediate color such as purple or pink have now been demanded. Here, the conventional methods have had a problem that the colors which can be developed, are rather limited, and it is difficult to satisfy the demand for various clear colors.
As methods for developing such various colors, JP-A-9-235141, JP-A-9-295834 and JP-A-10-877343 propose methods of forming colored films by means of a gold colloid. However, the colors of colored films obtained by these methods were a dark blue color or a bluish green color, and it was impossible to obtain a colored film having a clear blue color.
Further, JP-A-9-301743 proposes a method of forming a colored film having a clear blue color by means of a gold colloid. However, this method requires a double layer structure, and thus has had a problem that coating solutions have to be coated twice, thus leading to an increase of costs.
In view of the above problems, it is an object of the present invention to provide a colored film which presents a clear blue, green, bronze or gray color and which is excellent also in abrasion resistance and chemical resistance, by a single coating step, which can not be accomplished by the conventional wet methods, and a colored film-attached glass product and a process for producing such a product.